The human chain reaction that led to the atom bomb On December 26, 1898, Marie Curie announced the discovery of radium and observed that “radioactivity seems to be an atomic property.” A mere 47 years later, “Little Boy"exploded over Hiroshima. Before the Fallout is the epic story of the intervening half century, during which an exhilarating quest to unravel the secrets of the material world re...